1. Field of the Invention
This invention relates to packaging techniques for integrated-circuits and more particularly to techniques for protecting and maintaining the coplanarity of the leads of a flatpack package.
2. Prior Art
As the requirements for the number leads on integrated-circuit packages has increased, the size of the leads has decreased to the point where the leads are small and very fragile. In particular, the quad flat pack (QFP) plastic package has a large number of leads which are very small and fragile. The QFP package is a molded-plastic, flat-profiled, square-shaped package which has thin metal leads extending laterally from all four sides of the body of the molded-plastic package. The leads are bent down and terminate in a foot section, which is inclined slightly downward towards the tip of the lead. The leads are said to have a gullwing configuration, with the tips located at the ends of the wings. A QFP package is assembled to a circuit board by soldering the tips of the leads to a circuit board. A problem with this method of assembly is that it requires all of the tips of the leads to essentially be in the same mounting plane, that is, to be "coplanar." Coplanarity is a problem with the small and fragile gullwing leads of a QFP package because the leads can easily be displaced from coplanarity during shipping, handling, and installation. Because of the possibility of damage in shipping and handling of the QFP packages, customers of integrated-circuit manufacturers are reluctant to specify this type of package. In addition, the damage to the leads of QFP packages needs to be controlled.
During testing, the leads of a QFP package are maintained in proper position by being clamped in a test socket of a test fixture. This technique is expensive and not particularly useful when applied to shipping and handling of large numbers of QFP integrated-circuit packages.
Consequently, the need has arisen for some technique to prevent damage to the leads and to minimize damage to the leads of a QFP package during shipping, handling, and installation.